Conventionally, as a conventional head-up display, there is the one that is disclosed in Patent Literature 1, for example. Such a head-up display is composed of first and second display elements and a reflection-type hologram, and by the reflection-type hologram, image light of the first display element is transmitted, image light of the second display element is reflected, and the rays of image light from the first and second display elements are overlapped each other and then are directed to the transmission reflection surface. The first and second display elements are disposed so as to be different from each other in terms of a distance leading up to a viewer's eyes (a length of an optical path through which the image light passes (an optical path length)); and therefore, it is possible to cause a user to visually recognize a plurality of display images (virtual images) of which display distances are different from each other.
Incidentally, the head-up display that causes a person to visually recognize the plurality of virtual images of which display distances are different from each other can also be configured with the constituent elements as shown in FIG. 2. The head-up display shown in FIG. 2 has: a first display 110 to emit first image light 111; a second display 120 to emit second image light 121; a reflector 130 to reflect the first image light 111 that has been emitted from the first display 110 and the second image light 121 that has been reflected from the second display 120; and a concave reflector 140 to magnify the first image light 111 and the second image light 121 that have been reflected by the reflector 130 and then direct the rays of image light to a front window shield 200 which is mounted on a vehicle. A viewer can visually recognize a first virtual image 310, by the first image light 111 that has been reflected towards the viewer's side by the front window shield 200, and can also visually recognize a second virtual image 320 at a position which is lower in a vertical direction than that of the first virtual image 310, by the second image light 121 that has been reflected at the lower side more significantly than the position of the front window shield 200 on which the first image light 111 has been reflected. The second display 120 is disposed at a position which is more proximal to the viewer than that of the first display 110 in the travelling direction of the light (first image light 111, second image light 121). Therefore, the optical path length of the second image light 121 that is emitted from the second display 120 is smaller than the optical path length of the first image light 110 that is emitted from the first display 110, and the second virtual image 320 that is visually recognized by the second image light 121 is displayed at a position which is more proximal to the viewer than that of the first virtual image 310 that is visually recognized by the first image light 111.